Mapping the Lunar Wake Potential Structure With ARTEMIS Data.

Area of Science:

• Space Physics
• Plasma Physics
• Lunar Science

Background:

• Lunar wake refilling is explained by 1-D plasma expansion theory.
• Field-aligned wake potential is not directly measured, limiting statistical analysis.
• Previous studies lacked high-altitude statistical analysis of lunar wake potentials.

Purpose of the Study:

• Statistically analyze lunar wake potentials at high altitudes.
• Compare derived potentials with plasma expansion theories.
• Investigate the effects of interplanetary magnetic field orientation and solar wind electrons on wake structure.

Main Methods:

• Utilized data from the ARTEMIS mission's twin probes.
• Compared field-aligned electron distributions inside and outside the lunar wake.
• Expanded 1-D plasma theory to 2-D to model wake potential asymmetry.

Main Results:

• Derived wake potentials correlate with solar wind electron temperature and bulk flow velocity.
• Modeled and data-derived wake potentials show asymmetry, consistent with 2-D expansion.
• Ambipolar electric fields derived from models and data show good agreement.
• Solar wind strahl-electrons may cause a net potential difference across the lunar shadow.

Conclusions:

• ARTEMIS data supports and refines 1-D plasma expansion theory for lunar wake refilling.
• A 2-D model reveals wake potential asymmetry due to differing expansion times.
• The influence of strahl-electrons suggests wake effects may extend beyond current theoretical predictions.